U.S. patent number 6,042,105 [Application Number 08/953,489] was granted by the patent office on 2000-03-28 for method and apparatus for rotating an advancing sheet.
This patent grant is currently assigned to Oce-Technologies B.V.. Invention is credited to Johannes E. P. Peulen.
United States Patent |
6,042,105 |
Peulen |
March 28, 2000 |
Method and apparatus for rotating an advancing sheet
Abstract
A sheet advancing over a transport plane by pairs of transport
rollers is rotated through an angle of 90.degree. by retaining the
sheet at a point of rotation coupled with the releasing of one of
the transport roller pairs so that only the other transport roller
pair exerts a torque on the sheet. By disposing the other of the
transport roller pairs exerting the torque somewhat downstream of
the center of rotation, the sheet is maintained taut during
rotation.
Inventors: |
Peulen; Johannes E. P.
(Belfeld, NL) |
Assignee: |
Oce-Technologies B.V. (Venlo,
NL)
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Family
ID: |
19763694 |
Appl.
No.: |
08/953,489 |
Filed: |
October 17, 1997 |
Foreign Application Priority Data
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Oct 17, 1996 [NL] |
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1004297 |
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Current U.S.
Class: |
271/184; 271/185;
271/226 |
Current CPC
Class: |
B65H
5/18 (20130101) |
Current International
Class: |
B65H
5/18 (20060101); B65H 029/00 (); B65H 009/00 () |
Field of
Search: |
;271/184,185,226 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0248844 |
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Nov 1986 |
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JP |
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0132041 |
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May 1990 |
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JP |
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0270746 |
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Nov 1990 |
|
JP |
|
403152045 |
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Jun 1991 |
|
JP |
|
Primary Examiner: Terrell; William E.
Assistant Examiner: Park; Wonki K.
Claims
What is claimed is:
1. A method of rotating a sheet in the same plane as the direction
in which the sheet is being advanced, utilizing first and second
transport means operatively associated with a feed table for moving
said sheet on said feed table which comprises:
retaining the sheet at a center of rotation;
releasing the first of said transport means from active engagement
with the advancing sheet;
maintaining the second of said transport means in active engagement
with the advancing sheet causing the sheet to rotate about the
center of rotation, said second transport means, when viewed in a
direction transverse to the direction in which the sheet is being
advanced, being positioned at a fixed distance from the center of
rotation on a line between said second transport means and said
center of rotation, which line defines an angle .alpha. of between
75.degree. and 85.degree. with respect to the direction of the
advancing sheet.
2. The method of claim 1, wherein prior to and subsequent to the
execution of the rotation of the sheet, the sheet is advanced
through the second transport means which, when considered in the
direction of the advancing sheet, is in the same position as the
first transport means.
3. The method of claim 1, wherein the sheet is rotated through a
quarter of a revolution.
4. An apparatus for rotating a sheet in the same plane as the
direction in which the sheet is being advanced, which
comprises:
a feed table, defining a transport plane;
first and second transport means operatively associated with said
feed table for moving said sheet on said feed table;
means associated with said feed table for temporarily retaining the
sheet at a center of rotation;
means for releasing the first of said transport means from active
engagement with the advancing sheet;
means for maintaining the second of said transport means in active
engagement with the advancing sheet, causing the sheet to rotate
about said center of rotation, said second transport means, when
viewed in a direction transverse to the direction in which the
sheet is being advanced, being positioned at a fixed distance from
the center of rotation on a line between said second transport
means and said center of rotation, which line defines an angle
.alpha. of between 75.degree. and 85.degree. with respect to the
direction of the advancing sheet.
5. The apparatus of claim 4, wherein additional transport means are
operatively associated with said feed table upstream of said first
and second transport means, wherein the second transport means is
disposed a predetermined distance from said upstream, additional
transport means which is less than the length of the shortest sheet
for processing and the first transport means is disposed downstream
of the second transport means at a distance from said additional
transport means which is somewhat greater than the diagonal of the
largest sheet of rotation.
6. The apparatus of claim 4, wherein the retaining means is movable
between a first position which is free of an advancing sheet and a
second position which engages and retains the sheet at the center
of rotation, and wherein coupling means are provided between the
retaining means and the first and second sheet transport means,
whereby upon the movement of the retaining means from the first
position to the second position, the first transport means is moved
from a closed position to an open position.
7. The apparatus of claim 6, wherein the first and second transport
means comprises pressure rollers fixed on a common shaft, said
pressure rollers being disposed in opposing relationship to drive
rollers disposed beneath the feed table, and wherein the coupling
means contains an arm which moves the common shaft against the
spring action at the side of the pressure roller forming the second
transport means, upon movement of the retaining means from the
first inactive position to the second active position.
Description
BACKGROUND AND SUMMARY OF THE INVENTION
The present invention relates to a method of rotating a sheet
advanced in a straight line in the direction of the advance, in a
transport plane, by transport means, by retaining the sheet at a
center of rotation. A method of this kind is known from U.S. Pat.
No. 4,445,679 which describes a method in which during retention of
an advancing sheet at the center of rotation, a slip occurs between
the sheet transport means and the sheet. The sheet transport means
must be able to allow such a slip, e.g. by making the transport
means relatively smooth and/or by pressing it against the sheet
with a relatively minor force. In these conditions there is the
risk that when a sheet which has a relatively smooth surface is
rotated, the sheet will slip as a whole so that the required
rotation becomes incomplete. In the case of the rotation of a
relatively thin sheet and/or a sheet with a rough surface, the
sheet will not slip but will tear or crease.
Accordingly, the object of the present invention is to provide a
method and apparatus which does not have these disadvantages.
The present invention is characterized in that during the rotation
of the paper, the transport means forms solely a first transport
nip which, when considered in a direction transverse to the
direction in which the sheet is advanced in a straight line, is
situated at a fixed distance from the center of rotation on a line
between the first transport nip and said center of rotation which
line includes an angle of between 70 and 90.degree. with respect to
the direction of the advancing sheet. Consequently, a sheet can be
reliably rotated in a simple manner with the sheet transport means
operating continuously. Preferably, the angle is between 75 and
85.degree.. Consequently, the frictional force exerted by the sheet
transport means on the sheet during the rotation thereof has a
small component which keeps the sheet taut between the center of
rotation and the first transport nip so that creasing of the paper
is advantageously avoided, but without said small component
becoming so large that the sheet or the image thereon is
damaged.
Furthermore, preferably and prior to and subsequent to the
execution of a rotary movement, the sheet is also advanced through
a second transport nip which, when considered in the direction in
which the sheet advances in a straight line, is in an identical
position to the first transport nip. This minimizes the risk of
skewing before and after rotation.
The apparatus for performing the present method comprises retaining
means movable between a first position which are free of an
advancing sheet and a second position in which they retain the
sheet at the center of rotation, and is characterized in that
coupling means are provided between the retaining means and the
sheet transport means. Upon movement of the retaining means from
the first position to the second position, the sheet transport
means moves from a position in which the second transport nip is
closed to a position in which the second transport nip is open.
This is a simple construction to ensure that no slipping of the
transport nip occurs during the rotation of the sheet of paper.
If the first and second transport nips are formed by two pressure
rollers fixed on a common shaft and if the shaft is lifted at the
second transport nip when the second transport nip is opened, the
pressure roller is shifted upwards from the first transport nip to
form a punctiform first transport nip which further reduces the
slip in the first transport nip.
In an attractive embodiment of the apparatus according to the
present invention, the first transport nip is situated at a
predetermined distance from an upstream sheet feed nip which is
smaller than the length of the shortest sheet for processing and a
sheet discharge nip situated downstream of the first transport nip
is located at a predetermined distance from the sheet feed nip
which is somewhat greater than the length of the diagonal of the
largest sheet for rotation. Consequently, a sheet is rotated about
the center of rotation a short distance from the original leading
edge and the sheet edge, which becomes the leading edge after the
rotation of a quarter revolution is situated at a greater distance
downstream of the center of rotation so that the sheet can be
discharged relatively rapidly from the rotational zone.
BRIEF DESCRIPTION OF THE DRAWINGS
Other features and advantages of the invention will be explained
with reference to the accompanying drawings wherein:
FIG. 1 is a side elevation of the rotating device according to the
present invention disposed between a printing apparatus and a
folding device;
FIG. 2 is a cross-section on the line III--III in FIG. 2, shown in
a position in which a sheet advances in a straight line;
FIG. 3 shows the rotating device 1 of FIG. 2 in a position for
passing a sheet in a straight line;
FIG. 4 is a side elevation on the line IV--IV in FIG. 2 shown like
FIG. 3 in a position in which the sheet moves forward in a straight
line;
FIG. 5 is a cross-section on FIG. 3 shown in a position in which a
sheet undergoes a rotary movement;
FIG. 6 is a side elevation of FIG. 4 shown like FIG. 5 in the
position in which a sheet undergoes a rotary movement; and
FIG. 7 is a time/distance diagram of sheets during the rotary
movement according to the invention.
DETAILED DESCRIPTION OF THE INVENTION
The rotating device 1 shown in FIG. 1 is incorporated in a feed
table 2 of a folding device 3. Along the feed table 2, copy sheets
coming from a printing apparatus 4 are fed directly to the folding
device 3. The printing apparatus 4 is of the type in which sheets
of receiving material of different (standard) formats pass through
in the longitudinal direction, i.e. with their shortest side as the
leading edge, so that they can be readily folded into a packet.
As described in the above-mentioned U.S. Pat. No. 4,445,679, it is
preferable to feed a sheet having the dimensions of a folded packet
in the transverse direction to the folding device 3, i.e. a sheet
having its longest side as the leading edge. However, in the case
of the printing apparatus 4, in which a powder image is fused on a
receiving sheet by means of radiant heat, the radiation fuser
required for this purpose requires a minimum length when considered
in the sheet transit direction, for the radiation power to be
supplied. In the case when using a radiation fuser of this minimum
required length, the distance between the transport rollers at the
radiation fuser inlet and outlet may be too small to pass sheets
which do not require folding in the transverse direction. In this
case, this group of sheets, for example a group of sheets including
the A4 format, must be fed longitudinally through the printing
apparatus 4. For the sake of uniformity in inputting sheets it is
also logical to feed all sheet formats for processing to the
printing apparatus in the same orientation.
The folding device 3 is conventionally arranged to fold a supplied
sheet into a packet of dimensions corresponding to the smallest
standard format, e.g. the A4 format. The folding device of the type
shown in FIG. 1 is illustrated and described in greater detail in
European Patent 0 472 234. The folding device 3 of this type
comprises a first folding section 5, in which a sheet fed
longitudinally over the feed table 2 is folded zig-zag, the
distance between two consecutive folds corresponding to the
dimension of the shortest side of the smallest standard format,
e.g. a size of 210 mm in the case of the A4 format. In a second
folding section 6, the zig-zag folded sheet is folded in a
direction at right angles to the first folds to the size of the
longest side of the smallest standard format, i.e. to a size of 297
mm in the case of an A4 format. A copy sheet supplied in the
smallest standard format, e.g. an A4 format, can be left unfolded.
To this end, if such a sheet is passed through the folding device
3, so that the sheet can be placed on folded sheets so as to cover
the same, the sheet must be fed transversely to the folding device
3.
In order, in the case of a folding device 3 coupled on-line to the
printing apparatus 4, to allow both for the above requirements of
the printing apparatus 4 with respect to the orientation of the
smallest standard format, and the requirements of the folding
device 3 with respect to the orientation of the smallest standard
format, the feed table 2 is provided with a rotating device 1,
which will be described with reference to FIGS. 3 to 6, which
rotates a sheet of the smallest standard format fed longitudinally
through the printing apparatus, through a quarter revolution so
that the sheet can be fed transversely into the folding device
3.
The printing apparatus 4 is provided with a pair of outlet rollers
8. Downstream thereof is a deflector 9 which in the position shown
in FIG. 1 deflects a copysheet upwards for deposition onto a tray
10 sloping above the printing apparatus 4. The deflector 9 can also
be set to a position in which a copy sheet can be fed in the
direction of the feed table 2 of the folding device 3.
On the upstream side, the feed table 2 is provided with pairs of
transport rollers 11 and 12 while on the downstream side it is
provided with a pair of transport rollers 13. The pairs of rollers
form a plurality of transport nips distributed over the width of
the feed table 2, as shown in FIG. 2. Between the pairs of
transport rollers 12 and the pair of transport rollers 13, two
additional pairs of transport rollers 14 and 15 are disposed next
to one another which, in addition to advancing the sheets over the
feed table 2 for folding, also have a function in connection with
rotating a sheet, as will be described hereinafter.
Copy sheets printed in the printing apparatus 4, which are larger
than a group of sheets for passage unfolded by the folding device
3, are fed in a straight line over the feed table 2 by all the
transport roller pairs 11 to 15 in the direction indicated by arrow
16 in FIG. 2.
When a copy sheet is supplied belonging to a group of sheets having
a format requiring no folding, said sheet is turned through a
quarter revolution on the feed table 2 in the manner to be
explained hereinafter.
Rotation of a sheet on the feed table 2 is carried out when the
sheet reaches the transport nip between the pairs of transport
rollers 14 and 15. Rotation then takes place by retaining the sheet
near one of said transport nips, namely near the transport nip
formed by the transport roller pair 15, and releasing the transport
rollers 15 from one another so that transport rollers 14 rotate the
sheet about the center of rotation 17.
During rotation, the sheet must remain free from the transport
rollers 12 acting as input rollers and the transport rollers 13
acting as output rollers. In order to minimize the risk of the
sheet being fed in a skewed position by the pairs of transport
rollers 14 and 15 in the case of the transportation of a sheet
which does not require rotation, it is important that these pairs
of transport rollers 14 and 15 should be as far apart as possible
looking in a transverse direction to the transit direction 16. In
the case of an A4 sheet fed in the longitudinal direction and
having a width of 210 mm, the transport roller pairs can be up to
approximately 150 mm apart to ensure that any laterally shifted
sheet can be transported by the two pairs of transport rollers 14
and 15. In order to further ensure that a sheet is situated with
its central line substantially on the same line in the transit
direction 16 both before and after rotation through 90.degree., the
center of rotation 17 should be situated on a line which,
calculated from the center of the sheet for rotation, lies on a
line forming an angle of 45.degree. with the sheet sides. On the
basis of the above considerations, the distance between the
transport nips 14 and 15 and the location of the center of rotation
17 somewhat upstream of the nips 14 and 15, a sheet for rotation
must be transported with its leading edge over a distance A=75 mm
past the pairs of transport rollers 14 and 15 before rotation
starts. This means that for the rotation of the largest sheet for
rotation, which has a length B=325 mm, the transport rollers 14 and
15 must be located at a distance downstream of the input rollers 12
which should be at least B-A=325-75=250 mm. Since the distance
between the center of rotation 17 and the point of the leading
sheet edge situated furthest away from said center of rotation in
the case of the largest format of the group of sheets for rotation
in a size of 325.times.230 mm is equivalent to approximately 200
mm, the distance C between the transport roller pairs 14 and 15 and
the output rollers 13 should also be approximately 200 mm.
Consequently the distance between the input rollers 12 and the
output rollers should be at least B-A+C. In the case of the maximum
sheet format for rotation, i.e. 325.times.230 mm, this is therefore
325-75+200=450 mm. With some clearance between the leading and
trailing edge of the sheet and the output rollers 13 and input
rollers 12 respectively, a suitable free space for rotation between
the input and output rollers is 460 mm. For rotation of a sheet,
the center of rotation 17 on the feed table 2 is formed by pressing
the sheet with a rounded rubber cup against the feed table and
simultaneously or slightly prior thereto opening the transport nip
between the transport rollers 15 closest to the center of rotation
17. Given the continuous drive of the transport rollers 14 and 15,
the transport nip 14 situated furthest away from the center of
rotation 17 rotates the sheet about the formed center of
rotation.
The opening of the transport nip is effected by lifting close to
the pair of transport rollers 15 a shaft forming the connection
between the pressure rollers of the pairs of transport rollers 14
and 15 using a lever having at one end the rubber cup forming the
center of rotation and, at the other end a lug as will be explained
hereinafter with reference to the embodiment illustrated in FIGS. 3
to 5. As illustrated in the top plan view of the feed table 2, a
suitable location for the center of rotation 17 is on the
connecting line between the center point of the sheet at the start
of the rotation and the transport nip 15 for opening, the location
being a short distance from said nip e.g. 40 mm. By tipping the
connecting shaft between the pressure rollers of the pairs of
transport rollers 14 and 15 on opening of the nip 15, the other nip
14 will form a more punctiform nip, which is advantageous for
slip-free transportation during rotation of the sheet. Since the
punctiform transport nip 14 is also situated a short distance
downstream of the center of rotation 17 as viewed in the transit
direction, said transport nip 14 exerts a small tractive force on
the sheet, and this holds the sheet taut during rotation between
the nip 14 and the center of rotation 17.
FIGS. 3 and 4 show the rotating device 1 of FIG. 2 in a position
for passing a sheet in a straight line 16 through the rotating
device. This position is occupied both on the passage of a copy
sheet which has to be folded in the adjoining folding device 3 and
on the transport of a sheet for rotation prior to and following the
rotation of the sheet.
The rotating device 1 comprises two pairs of transport rollers 14
and 15. Each pair of transport rollers 14 and 15 consists of a
driven roller 20, 21 respectively fixed on a common drive shaft 22.
Rollers 20 and 21 project somewhat above the feed table 2 formed by
a plate. Each drive roller 20, 21 co-operates with a biasing roller
23, 24 respectively to form a transport nip. Biasing rollers 23, 24
are fixed on a common shaft 25 which fits by journals at its ends
into slots (not shown) extending vertically.
Near the shaft 25 is disposed a pin 26 fixed in the apparatus
frame. A T-shaped element 27 is fixed rotatably about said pin 26.
The upwardly projecting arm 28 thereof is provided with a U-shaped
recess in which a pin 29 fits which is fixed on an arm 30 movable
back and forth between two positions by means of a solenoid 31. One
arm 32 of the T-shaped element 27 is provided at its underside with
a rounded rubber cup 33 and another arm 34 is situated beneath the
shaft 25, so that arms 32 and 34 act as a lever. To perform a
rotary movement, the solenoid 31 is actuated so that the T-shaped
element 27 moves against spring action from the position shown in
FIGS. 3 and 4 to the position shown in FIGS. 5 and 6. In this
condition, arm 34 tilts shaft 25 up at the side of pressure roller
24 so that the transport nip between the rollers 21 and 24 is
opened. On rotation of the T-shaped element 27, the rubber cup 33
is also pressed against the sheet lying on the feed table 2. Thus
cup 33 forms the center of rotation 17 around which the sheet
rotates on the continuous transportation of the sheet through
transport rollers 20 and 23. As a result of the tilting of the
shaft 25, biasing roller 23 presses, as already stated, against the
drive roller 20 at substantially one point so that the angular
velocity at which the sheet rotates is determined by the radius R.
After the sheet has been turned through an angle of 90.degree., the
rotation time being ##EQU1## where V is the circumferential speed
of the drive roller 20, the solenoid 31 is de-energized so that
biasing roller 24 again forms a transport nip and the center of
rotation 17 is cancelled.
As shown in the distance/time diagram in FIG. 7, the sheet moves
forward during rotation, as a result of the situation of the center
of rotation 17 on the leading half of the sheet fed in the
longitudinal direction and at the side of the sheet so that the
distance between the center of rotation and the original leading
edge is less than the leading edge after rotation. As a result of
the continuous advance during rotation, a subsequent sheet can be
supplied a short distance S after the rotating sheet without
obstructing the latter, as will be apparent from FIG. 7.
In FIG. 7, the leading edge of a first sheet is indicated before
rotation by line 40 and after rotation by line 41. The trailing
edge is denoted by line 42 before rotation in FIG. 7 and by line 43
after rotation. For a subsequent sheet supplied at a distance S
from the first sheet, the leading edge is denoted by lines 44 and
45 respectively and the trailing edge by lines 46 and 47
respectively. The starting and stopping time of the rotation of the
first sheet is at the times 48 and 49 and for the next sheet is at
times 50 and 51.
The angle .alpha. which forms the included angle between the
direction in which the sheet moves straight ahead and the line
between the transport nip which remains continuously operative and
the formed center of rotation can vary within specific limits
without affecting good operation.
In the case of a 90.degree. angle .alpha., the transport force
operative in the transport nip is at right angles to the line
between said nip and the center of rotation of the sheet. Thus
under ideal conditions there is no slip in the transport nip. In
the case of a 70.degree. angle .alpha., the transport force in the
nip can be broken down into a rotating force at right angles to the
line between the nip and the center of rotation and a (small) force
operative in extension of said line and holding the sheet taut. If
the angle .alpha. is too small, the latter force may produce
unwanted slip in the transport nip. In the case of an angle .alpha.
between the above limits, e.g. an angle .alpha.=80.degree., a
compromise can be found in which the sheet is maintained taut
during rotation without appreciable slip occurring in the transport
nip, of course with some deformability of at least one of the
transport rollers in the transport nip.
The invention being thus described, it will be obvious that the
same may be varied in many ways. Such variations are not to be
regarded as a departure from the spirit and scope of the invention,
and all such modifications as would be obvious to one skilled in
the art are intended to be included within the scope of the
following claims.
* * * * *